It's not because they're "immature" or anything like that, and it's not a diss on anyone who still likes them, it's just that I tried to watch a new video of theirs and it just didn't hit me like it used to.
It's similar to what happened with me and the Nostalgia Critic (Tho admittedly with significant differences): I was a pretty big fan early on and for several years, but over time just fell off, started watching them more sporadically, before kinda just not keeping up with the new stuff anymore.
Given that all capitalist social media revolves around giving you Skinner Box dopamine or outrage fuel to lengthen the duration of each engagement so you can be served more ads, it's pretty clear why social media ended up where it is. I don't use TikTok/Instagram/whatever not because ooOooOoo China Bad but because if I'm going to look for addiction pathway chemicals I'll freeboot heroin without any ads being served to me.